Pressure altitude

• A. Height above the standard datum plane when 29.92 is set in the altimeter
• B. Height above the surface
• C. Altitude read directly from the altimeter
• D. Actual height above mean sea level

Answer: (A)

Pressure altitude is the height above the standard datum plane, defined as the imaginary surface where the standard atmosphere would have a pressure of 29.92 inHg. By setting the altimeter to 29.92 inHg, the instrument readings convert local pressure into a height above that fixed plane, providing a consistent reference for flight levels regardless of actual sea-level pressure. This is why it’s used for standardizing altitude separation at higher altitudes. Height above the surface is terrain elevation, not a fixed reference. The altitude read directly from the altimeter depends on the current pressure setting, not the standard 29.92, so it’s not pressure altitude unless that standard setting is used. Actual height above mean sea level is true altitude, which incorporates local pressure variations and temperature, not the fixed datum plane.